Elementary Particle Physics I Part 1 Particles and Standard Model Manfred Jeitler WS 2008/2009

1. Elementary Particle Physics IPart 1Particles and Standard ModelManfred JeitlerWS 2008/2009

2. Overview (1) • what are elementary particles? • the first particles • historical overview • a few formulas • the Dirac equation • relativistic kinematics • common units in elementary particle physics • the Standard Model • detectors • accelerators

3. Overview (2) • experimental elements of the Standard Model • the magnetic moment of leptons • fundamental symmetries and their violation • parity violation • CP-violation • T-violation • particle physics and cosmology • more particles • charm: J/ψ • beauty (bottom): Υ (“upsilon”) • τ • gauge bosons of electroweak interactions: W and Z • top • neutrino oscillations • beyond the Standard Model • what’s next? • Higgs - the missing link • supersymmetry • gravitational waves

4. e- the electron Thomson 1897

5. J.J. Thomson’s “plum-pudding model” of the atom ... the atoms of the elements consist of a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification, ...

6. e- p the proton Rutherford 1914 1897 1900-1924

9. e- g p the photon Einstein Planck Compton 1900-1924 1897

10. e- g p Chadwick n the neutron 1932 1914 1897 1900-1924

11. e- g p n e+ the positron (anti-matter) Anderson Dirac 1932 1947 1914 1897 1937 1900-1924

12. the Dirac equation

15. e- g p n e+ Who ordered this ? • Hess • Anderson, • Neddermeyer µ the muon 1937 1914 1897 1900-1924 1932

16. relativistic kinematics • elementary particles travel mostly at speeds close to speed of light • because their masses are small compared to typical energies • --> (almost) always use relativistic kinematics • “special relativity” is sufficient most of the time • remember a few basic formulae !

17. relativistic kinematics v 1/γ 1

18. the electron-volt (eV) + e- 1V - 1GeV = 1‘000‘000‘000 eV units: energy • meV: room temparature: ~ 30 meV • eV: ionisation energy for light atoms (13.6 eV in hydrogen) • keV: X-rays in heavy atoms • MeV: mass of electron me = 511 keV • GeV: mass of proton (~1GeV) • ~ 100 GeV: mass of W, Z • ~ 200 GeV: mass of top • TeV: range of present-day accelerators • 1019 GeV: ~ Planck mass

19. more units • velocity: speed of light • ~ 3 * 108 m/s • ~ 30 cm/ns • approximately, all speeds are equal to the speed of light in particle physics ! • all particles are “relativistic” • distance: fm (femtometer) • 1 fm = 10-15 m • sometimes also called “Fermi” • `hc ~ 200 MeV * fm

20. e- g p n µ e+ Yukawa Powell p the pion 1947 1937 1914 1897 1900-1924 1932

21. e- g p p n µ e+ n the neutrino Pauli Reines 1932 1947 1914 1897 1937 1900-1924

23. L e- g K n p µ n p e+ S Rochester, Butler, ... „strange“ particles 1947-... 1947 1914 1932 1897 1937 1900-1924

24. L e- g K n p p n µ e+ S In his Nobel prize speech in 1955, Willis Lamb expressed nicely the general attitude at the time: „I have heard it said that the finder of a new elementary particle used to be rewarded by a Nobel Prize, but that now such a discovery ought to be punished by a $10,000 fine.“ Lamb 1947-... 1947 1914 1932 1897 1937 1900-1924

25. n m KL Kc Sc W- KS B D t p0 h S0 3s 1s 2s J/y D* 4s f w r the particle zoo life time (s) 100000 e- p n 1s 1 ms E=1eV m 1 µs KL Kc pc Sc 1 ns W- KS B D t 10-15s p0 h S0 3s 1s 2s J/y 10-20s D* 4s f w W±, Zo r 10-25s mass (GeV/c2)

26. q q q q q g strong g t m u d u t u d c d d s d b u u e electromagnetic weak W, Z ? gravitation nm nt ne Wechselwirkungen Teilchen „Quarks“ „Leptonen“ Ladung stark 0 +2/3 -1 -1/3 schwach +1 0 +1/3 Proton Neutron

27. u g strong g t m t b c s u d e electromagnetic weak W, Z ? gravitation nt nm ne d Wechselwirkungen Anti-Teilchen Ladung stark 0 -2/3 +1 +1/3 schwach +1 Pion (p)

28. u u u u s s u u d d c u d D++ s L0 d K- p0 b D+ b  S+

29. t ne nm nt interactions u c strong g strong g electromagnetic u u d d u d d s b m t e weak W, Z ? gravitation weak force carriers = bosons (spin 1) the Standard Model fermions (spin ½) leptons quarks charge 0 +2/3 -1 -1/3 +1 0 proton neutron baryons

30. t ne nm nt u c g strong t d b c s u d s b m t e weak W, Z ? gravitation anti-particles leptons quarks interactions charge strong -2/3 nt ne nm 0 g +1 +1/3 e t electromagnetic m weak force carriers = bosons (spin 1)

31. the 4 fundamental interactions gravitation strong interaction electromagnetism weak interaction p+ K0 p-

33. lifetime and width • due to the uncertainty principle, the lifetime of a state (= unstable particle) and the accuracy, with which its mass (= rest energy) is reproduced at subsequent measurements, are correlated: Δt * ΔE ~ `h • lifetime can be measured directly for fairly long-lived states ( > 10-16 s) • width can be measured directly for short-lived states (becomes immeasurably small for long-lived states) • both properties can always be converted into each other: τ = `h / Γ Γ = `h / τ • remember: `hc ~ 200 MeV  fm c = 3 ~ 1023 fm/s  h ~ 2/3  10-21 MeV  s

34. cross section • defined via scattering probability W = n . σ • n ... number of scatterers in beam • σ ... cross section of individual scatterer • naive picture: each scatterer has a certain “area” and is completely opaque • absorption cross section • can also be used for elastic scattering ... • into certain solid angle dΩ: dσ/dΩ • ... or particle transformation • differential cross section for a certain reaction • unit: “barn”: (10 fm)2 = 100 fm2 = 10-28 m2 = 10-24 cm2

35. fundamental interactions

36. Feynman diagrams for electromagnetic interactions

37. Flipping around space, time, and charge

38. Feynman diagramsfor Weak interactions

41. experimental setup for measuring deep-inelastic electron-proton scattering (from Robert Hofstadter’s Nobel prize lecture, 1961)

42. color charge Apart from their electric charge, quarks also have “color charge”. The particles which convey this interaction and keep the quarks together are called gluons.

43. q q u q q d q q q mesons baryons • Free quarks have never been observed, they always appear in bound states (quark confinement). • 2 types of bound states are observed: • 3 quarks of three different colors: baryons • 2 quarks of a color and its anticolor: mesons

44. Feynman diagramsfor Strong interactions

45. 3-jet event (Aleph experiment, LEP Collider, CERN, Geneva, Switzerland)

46. u c u u u d d d p+ K-  D+ d u d b ... mesons s b ... u u baryons s u u d proton neutron D++ L0 atom nucleus He nucleus (a-particle) matter

47. Robert Hofstadter (Nobel prize lecture, 1961)

48. e e- e- p µ p p e+ e+ nm nm What do we observe? decays & scattering ne decay  26 ns  2200 ns K K scattering p